In general, a nano gap is an electrode in which metal structures have a gap of tens of nanometers to hundreds of nanometers and may be used in researches on the electrical properties of a nano-sized structure or as a sensor for sensing a chemical material or a biological material in an ultra-fine amount. In particular, a nano gap is essential in measuring a variation of electrical properties at a molecular level.
A conventional technology for manufacturing a nano gap may include a method of generating a gap at a certain location of a metal wire by using electromigration (Appl. Phys. Lett 75, 301), a method of using an electron-beam lithography (Appl. Phys. Lett 80, 865), and a method of depositing metal thin films by using soft substrates (KR2013-0125183).
However, the method of manufacturing the nano gap via electromigration is based on a principle in which an electric current flows in a metal wire having a line width of about hundreds of nanometers or less and atoms in the metal wire collides with electrons and migrate to generate nano gaps. Therefore, it is difficult to control a size of the nano gap and a location where the nano gap is formed.
In the method of manufacturing the nano gap via electron-beam lithography, a size of the nano gap and a location where the nano gap is formed may be accurately controlled since a pattern is directly drawn by an electron beam. However, manufacturing a nano gap by this method is expensive.
According to the method of manufacturing the nano gap on a flexible substrate via a tensile strain, a size or a location of the nano gap cannot be controlled, productivity degrades, and nano gaps having uniform performance and characteristics may not be obtained.
On the contrary, a method in which a spacer is located at a side of a first electrode and a second electrode is formed, and then, the spacer is removed to form a nano gap electrode has been suggested. However, manufacturing processes are complicated and it is difficult to adjust a width of a nano gap, and moreover, a plurality of nano gap electrode devices may not be manufactured at a time.
In addition, an electrochemical deposition method may be used, that is, metal electrode patterns spaced apart by a relatively large gap are formed on a certain substrate, an electric power is supplied to the metal electrode patterns with the substrate entirely immersed into a certain electrolyte so that an electrode material layer is deposited on a surface of the metal electrode patterns and is grown to reduce a width of the gap and generate a nano gap. However, the manufacturing processes are complicated and it is difficult to adjust a size of the nano gap.
In addition, according to a method of manufacturing nano gap by using a shadow mask, in which a nanostructure such as a nanotube is placed and a metal material is deposited so as to generate a nano gap as large as a size of the nanostructure, a size of the manufactured nano gap is dependent upon a size of the nanostructure and it is difficult to form the nano gap at a desired location.
As described above, the nano gaps manufactured by the prior art may not have uniform quality, and thus, when a nano gap is used as a sensor for detecting a target material or gas, a large error between a magnitude of a response signal and a signal range may occur. Thus, the nano gap used as a sensor may not have uniform performance and may have low reliability, and accordingly, it is difficult to mass produce and commercialize nano gaps formed using these methods.